Handle fallback font size in text appearances

If we end up using our fallback font size when generating appearances
for text fields, reflect that in the Tf operator used in the
appearance stream.

1 files changed, 35 insertions, 1 deletions

diff --git a/libqpdf/QPDFFormFieldObjectHelper.cc b/libqpdf/QPDFFormFieldObjectHelper.cc
index da49505a..38755388 100644
--- a/libqpdf/QPDFFormFieldObjectHelper.cc
+++ b/libqpdf/QPDFFormFieldObjectHelper.cc
@@ -715,17 +715,23 @@ class TfFinder: public QPDFObjectHandle::TokenFilter
     virtual void handleToken(QPDFTokenizer::Token const&);
     double getTf();
     std::string getFontName();
+    std::string getDA();
 
   private:
     double tf;
+    size_t tf_idx;
     std::string font_name;
     double last_num;
+    size_t last_num_idx;
     std::string last_name;
+    std::vector<std::string> DA;
 };
 
 TfFinder::TfFinder() :
     tf(11.0),
-    last_num(0.0)
+    tf_idx(0),
+    last_num(0.0),
+    last_num_idx(0)
 {
 }
 
@@ -734,11 +740,13 @@ TfFinder::handleToken(QPDFTokenizer::Token const& token)
 {
     QPDFTokenizer::token_type_e ttype = token.getType();
     std::string value = token.getValue();
+    DA.push_back(token.getRawValue());
     switch (ttype)
     {
       case QPDFTokenizer::tt_integer:
       case QPDFTokenizer::tt_real:
         last_num = strtod(value.c_str(), 0);
+        last_num_idx = DA.size() - 1;
         break;
 
       case QPDFTokenizer::tt_name:
@@ -754,6 +762,7 @@ TfFinder::handleToken(QPDFTokenizer::Token const& token)
             // insane things or suffering from over/underflow
             tf = last_num;
         }
+        tf_idx = last_num_idx;
         font_name = last_name;
         break;
 
@@ -769,6 +778,30 @@ TfFinder::getTf()
 }
 
 std::string
+TfFinder::getDA()
+{
+    std::string result;
+    size_t n = this->DA.size();
+    for (size_t i = 0; i < n; ++i)
+    {
+        std::string cur = this->DA.at(i);
+        if (i == tf_idx)
+        {
+            double delta = strtod(cur.c_str(), 0) - this->tf;
+            if ((delta > 0.001) || (delta < -0.001))
+            {
+                // tf doesn't match the font size passed to Tf, so
+                // substitute.
+                QTC::TC("qpdf", "QPDFFormFieldObjectHelper fallback Tf");
+                cur = QUtil::double_to_string(tf);
+            }
+        }
+        result += cur;
+    }
+    return result;
+}
+
+std::string
 TfFinder::getFontName()
 {
     return this->font_name;
@@ -843,6 +876,7 @@ QPDFFormFieldObjectHelper::generateTextAppearance(
     tok.write(QUtil::unsigned_char_pointer(DA.c_str()), DA.length());
     tok.finish();
     double tf = tff.getTf();
+    DA = tff.getDA();
 
     std::string (*encoder)(std::string const&, char) = &QUtil::utf8_to_ascii;
     std::string font_name = tff.getFontName();